Hydraulic power apparatus

ABSTRACT

Hydraulic apparatus to drive a number of fluid-actuated power components wherein a number of circuits, at least certain of which are provided with pumps of the variable flow type, are coupled to a common filter unit which not only filters the fluid flowing to the pump inlets but also assures that the pump inlet pressures will be at positive values to thereby prevent structural damage to the pumps, such as by cavitation, while at the same time, each pump is able to meet the fluid demands of its power component. A heat exchanger coupled to the circuits maintains the heat content of the fluid in the circuits within a safe temperature range. The apparatus is especially adapted for use with a vehicle having drive means, a power tool shiftably mounted on the vehicle, and power structure for shifting the power tool into any one of a number of operative positions.

United States Patent 4 4 emo [72] Inventors Donald R. Vaughan [56] References Cited E1 li 12 .3 g 8 M B I UNITED STATES PATENTS a acon, ox ayor 44 4 $52422; 2422; 5:12,, 23, 5: 1 pp No 24,403 g [22] Filed Mar. 13, 1970 Primary ExaminerEdgar W. Geoghegan Division of Ser. No. 643.979, June 6, 1967 Attorney-Townsend & Townsend Patent No. 3,507,125 [45] Patented July 6, 1971 ABSTRACT: Hydraulic apparatus to drive a number of fluidactuated power components wherein a number of circuits, at least certain of which are provided with pumps of the variable flow type, are coupled to a common filter unit which not only filters the fluid flowing to the pump inlets but also assures that the pump inlet pressures will be at positive values to thereby prevent structural damage to the pumps, such as by cavitation, while at the same time, each pump is able to meet the fluid de- [54] POWER APP TUS mands of its power component. A heat exchanger coupled to mwing the circuits maintains the heat content of the fluid in the cir- [52] US. Cl 60/52, cuits within a safe temperature range. The apparatus is espe- 92/78, 60/97 cially adapted for use with a vehicle having drive means, a [5 1] Int. Cl FlSb 21/04 power tool shiftably mounted on the vehicle, and power struc- [50] Field of Search 60/52 VS, ture for shifting the power tool into any one of a number of 52, 53, S4, 97 P, DIG. 5', 92/78 operative positions.

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INVENTORS DONALD RVAUGHAN CARL J. meow ATTORNEYS HYDRAULIC PUWER APPARATUS This is a division of application, Ser. No. 643,979 filed June 6, 1967, now US. Pat. No. 3,507,125, issued Apr. 21, 1970.

This invention relates to improvements in hydraulic circuitry of the type adapted for delivering fluid power to fluid actuated external load devices .and, more particularly, to hydraulic apparatus for providing the complete power system of a unit having a number of independently operated power components.

The present invention is directed to hydraulic apparatus utilizing a number of fluid pumps coupled to respective external load devices for performing a number of independent functions. While the invention can be used for a number of different purposes, it is especially adapted for use with a vehicle of the type described in the aforesaid application wherein the vehicle has drive means for propelling it forwardly, a power tool shiftably mounted on the vehicle and adapted to perform a certain function, and power structure for moving the power tool relative to the vehicle into any one of a number of working positions. Certain of the fluid pumps will be of the variable flow type and, since the fluid demands on these pumps will vary to meet different operating conditions, means is provided to assure not only that the fluid supplied to the pump inlets will be filtered, but also that the fluid will, at all times, be supplied at positive pressures to prevent cavitation or other structural damage to the pumps. To this end, the apparatus includes a filter unit common to all of the circuits of the apparatus with the filter unit including a filter for filtering the fluid to the pump inlets and eductor means disposed to supply reserve fluid to the circuits from a fluid reservoir as the fluid demand arises and to drive the fluid through the filter to thereby assure that fluid pressure at all pump inlets will be at positive values.

Since the filter unit is common to all of the circuits, it can be more conveniently and readily removed for cleaning and replacement than if individual filters are provided for the various circuits. Moreover, space limitations are often a factor in the construction of a system utilizing apparatus of this type. Thus, the single filter unit for the various circuits minimizes the space required. Also, the filter unit can utilize one or more eductors and filters designed in accordance with the capacities of the various pumps of the circuit.

The eductor of the filter unit includes a suction device connected by a conduit to the reservoir. Since the filter unit is common to all of the pumps, it is necessary to prevent reverse flow of fluid to the reservoir. Thus, a check valve is inserted in the conduit connecting the suction device with the reservoir. This allows fluid flow only front the reservoir to the suction device without impairing the demand for fluid from the reservoir itself.

Most conventional hydraulic circuits do not use a filter on the inlet side of a pump unless a precharge pump is used to drive fluid through the filter. The conventional systems generally filter the fluid on its return to a tank or reservoir. Thus, any contaminant that enters the tank must pass through the circuit before it is filtered.

The present invention eliminates this problem and, also, does not require a precharge pump. By eliminating a precharge pump, there is a considerable saving in the space requiredfor the hydraulic circuitry. To this end, one or more eductors are utilized to drive fluid through the filters of the various pumps and to assure that the fluid pressure at the pump inlets will be positive rather than negative. The eductor capacity is matched to the fluid volume requirements. One or more eductors can be used as desired and each eductor is constructed so that it will allow a certain percentage of the return fluid to pass through a heat exchanger and then to the fluid reservoir associated with the eductor. This maintains a good balance of fluid passing through the heat exchanger and assures that the fluid will continue to be at safe operating temperatures for all operating conditions of the apparatus.

It is the primary object of this invention to provide hydraulic apparatus for use in supplying the power to a system having a number of independently actuated external loads wherein the apparatus includes a number of circuits having a common filter unit for supplying filtered fluid to the pump inlets at positive pressures so that at least certain of the pumps can be of the variable flow type to permit substantially automatic control of the loads.

Another object of this invention is to provide apparatus of the type described for a vehicle having drive means, a power tool shiftably mounted on the vehicle, and power structure for moving the power tool into any one of a number of working positions on the vehicle so that the components of the vehicle may be operated independently of each other to perform their respective functions while at the same time, filtered fluid will be available at positive pressures to the pump inlets of the circuits to ensure substantially uninterrupted operation of the vehicle.

A further object of this invention is to provide hydraulic apparatus of the aforesaid character wherein the fluid pump of one of the hydraulic circuits is of the variable flow type and is responsive to the pump inlet pressure of another circuit, whereby the other circuit can be used to actuate the power tool while the first-mentioned circuit can be used to actuate the drive means of the vehicle in accordance with the work that must be expended to accomplish the function of the power tool when the same is under operating conditions.

Other objects of this invention will become apparent as the following specification progresses, reference being had to the accompanying drawings which set forth a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a schematic view of the hydraulic apparatus;

HO 2 is a side view, partially schematic, of the filter unit of the apparatus; and

FIG. 3 is a front elevational view of the filter unit of FlG. 2.

Hydraulic apparatus 10 shown schematically in FIG. 1 inclucles a first hydraulic circuit 12, a second hydraulic circuit M, and a third hydraulic circuit 16. As will hereinafter be made clear, apparatus 10 is especially adapted for use in providing the complete power system for a vehicle having drive means, a power tool mounted on the vehicle for move ment into any one of a number of operative positions, and power structure coupled with the tool for positioning the same. However, it will be clear to those skilled in the art that apparatus 10 is adapted for other uses as well.

Circuit 12 includes a pump 18 of the variable flow type, a flow divider unit 20 coupled to pump It to receive fluid therefrom. A pair of four-way valves 22 and 24 are coupled with flow divider 20 and control respective hydraulic motors 26 and 28 so that the latter can be driven in either ofa pair of opposed directions. A lock valve 30 is provided for each of the motors 26 and 28 and a flow control] device 32 is in the fluid flow circuit of motor 26. Device 32 comprises a structure having a variable orifice for limiting the flow to motor 26 in a manner and for a purpose to be described. The fluid outlets of valves 22 and 24 are coupled by a conduit 34 to a filter unit broadly denoted by the numeral 36. An on-off valve 38 is coupled to the forward lines of the conduits leading to motors 26 and 28 from valves 22 and 24, respectively. The purpose of valve 38 will be made clear hereinafter.

Second circuit 14 includes a fluid pump 40 of the variable flow type having its outlet coupled to the fluid inlet of a fluid motor 42. The outlet of motor 42 is coupled by a conduit 44 to filter unit 36.

Each of pumps 18 and 40 has a pressure compensator 46 which automatically varies the volume rate of flow of fluid from the pump in response to a predetermined pressure. A conduit 48 couples the compensators together. Variations in the fluid pressure at the inlet of motor 42 has an effect on the compensator of pump 40, which compensator will control the compensation of pump w by limiting the flow of fluid to divider 20 in response to an increase in pressure at the inlet of pump 42. Thus, the volume rate of flow of fluid to motors 26 and 28 can be a function of the fluid pressure at the inlet of motor 42.

Third circuit 16 includes a fluid pump 50 coupled at its out let to a bank of four-way valves 52, 54, 56 and 58. This valve bank is coupled to a crossover valve 60 which has a conduit 62 coupling it with filter unit 36. Crossover valve 60 is also coupled to another valve 64 which controls fluid flow through a double acting fluid piston and cylinder assembly 66 controlled by a lock valve 68.

Filter unit 36 is designed to match the required fluid needs in accordance with the capacities of pumps 18, 40 and 50. Filter unit 36 includes a housing 70 having one section 72 defining a fluid reservoir and a second section 74 which receives fluid from one or more eductors 76 coupled to return lines from respective pumps. As shown in FIG. 2, one of the eductors 76 is coupled to the return conduit 34 of circuit 12 and includes a suction device 78 having a venturi 80 in communication with a bore 82 which interconnects reservoir 72 with section 74 (FIG. 2). A conduit 84 communicates with the throat 86 downstream of the venturi 80 and the interior of reservoir 72. A ball check valve 88 in conduit 84 allows fluid flow only from reservoir 72 to throat 86.

. Filter unit 36 also includes one or more filters 90 disposed in section 74. Filter 90 may be of any construction but, for purposes of illustration, includes a wire mesh surrounding a pipe 92 having perforations 94 within the corresponding filter 90. As fluid passes through the filter, it is caused to enter pipe 92 through perforations 94 from whence it can flow outwardly of housing 70 through respective outlets 96 coupled to the inlets of the corresponding pumps.

Each eductor 76 has a relief port 98 upstream of venturi 80 (FIG. 2) and a relief valve 100 is disposed in a conduit 102 communicating with port 98, the conduits 102 being coupled to a conduit 104 which leads to a heat exchanger 106. A conduit 108 interconnects heat exchanger 106 and reservoir 72 (FIG. 1).

In FIG. 1, three eductors are shown, there being an eductor for each pump, respectively. However, a single eductor could operate for all of the pumps if properly designed. in complicated circuits, any number of eductors may be applied. As additional eductors are used, they work in sequence to increase the flow so that when some of the circuits are not in use, energy is not expended for maintaining afluid supply.

Each eductor operates to draw fluid by suction out of reservoir 72 as the fluid demand arises. The suction is caused by the increased fluid velocity due to venturi 80. By the use of ball check valve 88, fluid cannot return to the reservoir from the eductors.

ln matching an eductor to a given fluid flow, it has been found that if only 50 percent of the flow is used through the eductor, that it will pick up fresh fluid from the reservoir to replenish the fluid directed through port 80. By directing a portion of the fluid to the heat exchanger and then returning it to the reservoir, the system is given a greater response in that the eductor drives the filter at a far lower volume rate of flow than if the total volume were to be used. Also, this maintains a good balance of circuit fluid passing through the heat exchanger to cool the fluid. To increase or decrease the fluid flow to the heat exchanger, the size of the eductors can be varied.

To illustrate the operation of apparatus 10, it will hereinafter be described with respect to a vehicle of the type set forth in the above-mentioned pending patent application. The vehicle has rightand left-hand drive or propelling units, such as ground'engaging wheels or tracks, and motors 26 and 28 will be coupled to these units for advancing them. Thus, the vehicle can be driven forwardly, can be turned or can be reversed by proper manipulations of valves 22 and 24.

The power tool will be mounted for rotation and translation relative to the vehicle, and for purposes of illustration only, will be of the type used to bore through the ground for cable laying purposes. To this end, motor 42 will be coupled to the tool for rotating the same and the motors (not shown) associated with valves 52, 54 and 56 will be used for translating the power tool. The speed of rotation of the tool can be controlled by manually stroking variable flow pump 40. Also, the volume rate of fluid flow to motors 26 and 28 will be controlled in response to the fluid pressure at the inlet of motor 42 through the use of compensators 46.

Circuit 16 is the control circuit for the power tool whereby it can be shifted into any one of a number of operating positions. For purposes of illustration only, the various valves 52, 54 and 56 operate to respectively raise and lower the tool, change the attitude of the tool, and shift the same laterally relative to the vehicle. Valve 58 is provided for controlling other structure on the vehicle, such as a bulldozer which is to be raised and lowered.

Circuit 16 also provides for the depth to which the power tool penetrates the ground. To this end, valve 64 is a four-way valve with all ports open in its center or neutral position. This valve is activated by a shoe riding on the ground adjacent to the power tool when the latter is in an operative position. The fluid from the ports of valve 64 pass through a lock valve 68 and the cylinder lines of assembly 66 are tied commonly with the manual valve lines coming from valve 52. In neutral, the cylinder ports in the main valve bank are closed. Lock valve 68 will not allow fluid out of the cylinders unless fluid pressure is applied from depth control valve 64. Thus, terrain changes will be sensed by the shoe, which will actuate assembly 66 in the corresponding direction to raise or lower the power tool through valve 52. When the crossover valve 60 is passing fluid to the corresponding eductor instead of valve 64, lock valve 68 stops any flow from assembly 66. If depth control valve 64 is in the circuit and the operator attempts to operate manually, the moment the manual valve lifts the sensing shoe off the ground, depth control valve 64 will shift and open lock valve 68 to offset the direction that the operator is trying to do manually. When control valve 64 is locked out by crossover valve 60, assembly 66 can be manually operated by valve 52.

The eductor receiving fluid, from conduit 62 will be matched to pump 50 and for purposes of illustration only, will pass about 4 /2 gallons per minute at a pump outlet pressure of 65 psi. About 3% gallons per minute will pass through the corresponding port for flow to and through heat exchanger L06.

Pumps 18 and 40 are preferably directly driven from a suitable power source, such as a gasoline engine or the like. Since both pumps can be manually stroked to a center neutral position so that no fluid flows therefrom, there is no need for a clutch to disengage and to start the engine. Thus, the pumps can be stroked to neutral and the engine started to bring it up to the proper operating condition. Pump 18 can be stroked to give any desirable forward speed to the vehicle. In the event that pump 40 is not operating, pump 18 will be automatically stroked toward neutral if the outlet pressure thereof exceeds the maximum setting of its own compensator 46. The operator cannot manually override this condition but must take other action to relieve it.

When pump 18 begins to pump fluid, the fluid flows through divider 20 and to valves 22 and 24. Lock valves 30 prevent motors 26 and 28 from overrunning which could cause cavitation. Motor 26 on the left-hand side of the circuit operates differently because of the torque on the vehicle caused by the rotation of the power tool. This torque ordinarily gives an assist to the left side of the vehicle but by putting flow control 32 and valve 38 in circuit 12, this torque effect can be overcome; As the torque forces the left side of the vehicle, the return fluid will shut down the lock valves if it is extreme but, if it is normal, the flow control will induce enough restriction to offset the torque. Flow control 32 is variable so as to match to various forward speeds and ground conditions. The fluid upon leaving the valves 22 and 24 enters an eductor in filter unit 36. For relatively small flow rates, this return could go directly to one of the filters rather than to an eductor.

Apparatus provides full automatic control of the movement of the vehicle in accordance with the fluid pressure at the inlet of motor 42. The apparatus also provides a means to drive fluid at a positive pressure through a filter medium and to deliver the fluid at positive pressures to the inlet means of one or more fluid pumps which can be of the variable flow type. The apparatus provides a means for delivering filtered oil to meet various demands while maintaining an adequate supply to the heat exchanger to assure the proper heat content of the fluid in the various circuits. Finally, the apparatus can be used to maintain a constant depth of the tool in the ground and to allow the operator to take over manually.

What we claim is:

l. Hydraulic apparatus comprising: a pair of hydraulic circuits; and a filter unit common to said circuits; each circuit including a fluid pump having a fluid inlet and a fluid outlet, a fluid-actuated power device having a fluid inlet and a fluid outlet, first conduit means coupling said outlet of the pump to said inlet of the device, second conduit means coupling said outlet of the device with said inlet of the pump, said filter unit including filter means across said second conduit means for filtering the fluid flowing to said pump inlet, a fluid reservoir, and eductor means coupled to said reservoir and to said second conduit means between said device and said filter means for drawing fluid into said second conduit means from said reservoir responsive to the fluid pressure at said filter means and third conduit means placing said reservoir in fluid communication with said second conduit means at a location on the latter between said eductor means and said device, whereby fluid in the circuit may return to the fluid demand of said pump decreases.

2. Hydraulic apparatus as set forth in claim I, wherein said eductor means includes a check valve disposed to prevent fluid flow from said reservoir to said second conduit means the reservoir when v until a predetermined fluid flow rate has been established in said second conduit means.

3. Hydraulic apparatus as set forth in claim 1, wherein the fluid pump of one of said circuits has actuatable means for varying the volume rate of flow of fluid from said output thereof, and means responsive to the fluid pressure in the first conduit means of the other circuit for actuating said varying means of the pump of said one circuit.

4. Hydraulic apparatus as set forth in claim 1, wherein is provided a heat exchanger in said third conduit means for changing the heat content of the fluid flowing therethrough to said reservoir.

5. Hydraulic apparatus as set forth in claim 1, wherein is provided a relief valve in said third conduit means to limit the fluid flow therethrough.

6. Hydraulic apparatus comprising: a fluid pump having a fluid inlet and a fluid outlet; a fluid-actuated power device having a fluid inlet and a fluid outlet; a first conduit connecting said outlet of the pump to said inlet of said device; a second conduit connecting said outlet of the device with said inlet of the pump; a filter across said second conduit to filter the fluid passing therethrough toward said pump; a fluid reservoir; an eductor including a suction element across said second conduit; a third conduit placing said suction element in fluid communication with said reservoir; a check valve in said third conduit and disposed to permit fluid flow only from said reservoir to said suction element; and a fourth conduit placing said reservoir in fluid communication with said second conduit at a location between said suction element and said outlet of the device.

7. Hydraulic apparatus as set forth in claim 6, wherein is provided a relief valve in said fourth conduit to limit the fluid flow therethrough. 

1. Hydraulic apparatus comprising: a pair of hydraulic circuits; and a filter unit common to said circuits; each circuit including a fluid pump having a fluid inlet and a fluid outlet, a fluidactuated power device having a fluid inlet and a fluid outlet, first conduit means coupling said outlet of the pump to said inlet of the device, second conduit means coupling said outlet of the device with said inlet of the pump, said filter unit including filter means across said second conduit means for filtering the fluid flowing to said pump inlet, a fluid reservoir, and eductor means coupled to said reservoir and to said second conduit means between said device and said filter means for drawing fluid into said second conduit means from said reservoir responsive to the fluid pressure at said filter means, and third conduit means placing said reservoir in fluid communication with said second conduit means at a location on the latter between said eductoR means and said device, whereby fluid in the circuit may return to the reservoir when the fluid demand of said pump decreases.
 2. Hydraulic apparatus as set forth in claim 1, wherein said eductor means includes a check valve disposed to prevent fluid flow from said reservoir to said second conduit means until a predetermined fluid flow rate has been established in said second conduit means.
 3. Hydraulic apparatus as set forth in claim 1, wherein the fluid pump of one of said circuits has actuatable means for varying the volume rate of flow of fluid from said output thereof, and means responsive to the fluid pressure in the first conduit means of the other circuit for actuating said varying means of the pump of said one circuit.
 4. Hydraulic apparatus as set forth in claim 1, wherein is provided a heat exchanger in said third conduit means for changing the heat content of the fluid flowing therethrough to said reservoir.
 5. Hydraulic apparatus as set forth in claim 1, wherein is provided a relief valve in said third conduit means to limit the fluid flow therethrough.
 6. Hydraulic apparatus comprising: a fluid pump having a fluid inlet and a fluid outlet; a fluid-actuated power device having a fluid inlet and a fluid outlet; a first conduit connecting said outlet of the pump to said inlet of said device; a second conduit connecting said outlet of the device with said inlet of the pump; a filter across said second conduit to filter the fluid passing therethrough toward said pump; a fluid reservoir; an eductor including a suction element across said second conduit; a third conduit placing said suction element in fluid communication with said reservoir; a check valve in said third conduit and disposed to permit fluid flow only from said reservoir to said suction element; and a fourth conduit placing said reservoir in fluid communication with said second conduit at a location between said suction element and said outlet of the device.
 7. Hydraulic apparatus as set forth in claim 6, wherein is provided a relief valve in said fourth conduit to limit the fluid flow therethrough. 